Forest Fire Simulation Principles, Models and Application

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Forest Fire Simulation - Principles, Models and
Application

• L. Halada, J. Glasa, P. Weisenpacher
• Institute of Informatics
• Slovak Academy of Sciences

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Motivation - Forest Fires in Slovenský Raj
National Park 1994-1998
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Scientific Goals

• Further improvement of the computational model
  applied.
• To test methods of data analysis to precise the
  input parameters.

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Practical Goals

• Creation of a decision support system for a
  protection of selected areas.
• As a means provided to a training centre for
  practical implementation.
• As a tool for universities, ecosystem
  institutions, insurance companies, etc.

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Basic Principles - Conservation Equations
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Difficulties of the Problem

• Complex structure of the wildland forest geometry
• Complexity of chemical and physical dynamics of
  combustion
• Turbulence
• Meteorological conditions and their dependence on
  fire-induced air flows

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Envelope Models Huygens principle

• A fire ignited at a point will expand under
  constant conditions and homogeneous fuel as an
  ellipse
• Elliptic shape of fire depending on wind, slope
  and fuel
• Secondary fires grow from the each point of the
  actual fire perimeter
• Envelope that encompasses all small ellipses
  gives a fire perimeter in the next instant

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Principles of the Propagation in Envelope Model
Step I

• Local fire

• x(?,t) a. t . cos(?)
• y(?,t) c. t b. t . sin(?)
• 0 ? ? ? 2?
• bc, b-c, a forward, backward and lateral rate
  of fire spread

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Principles of the Propagation in Envelope Model
Step II

• Huygens principle

• Ellipses generated in points (x(i), y(i)), i
  1,2 .
• New fire front is defined by the envelope of the
  ellipses generated at each point of the fire line.

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Huygens principle

• Constant wind direction, variable fuel

• Changed wind direction, constant fuel

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Envelope Model - Practical Application

• Correction to non-zero slope
• Evaluation of the value ? the angle of the
  resultant wind-slope vector (Rothermel 1972)
• Length to breath (LB) and head to back (HB) ratio
  (Anderson 1983) of the ellipse

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Envelope Model - Practical Application

• Steady-state fire spread rate (Albini 1976,
  Rothermel 1972)
• R - steady state spread rate IR -
  reaction intensity,
• p - propagating flux ratio ?b - bulk
  density
• e - effective heating number Qi - heat of
  pre-ignition
• FW - wind coefficient FS -slope
  coefficient

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Envelope Model - Practical Application

• Semi-axes of the ellipse

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Envelope Model - Differential Equation for
Fireline Propagation

• Fireline is represented by a polygon
  consisting of series of 2D vertices

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FARSITE (Fire Area Simulator) developed by M. A.
Finney (1994)

• program using envelope model for 2D numerical
  forest fire growth simulation in given area with
  given
• weather conditions
• fuel type
• topography

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The Use of FARSITE

• Simulation of past fires reconstruction A
  comparison of the simulated fires with the known
  fire growth pattern. Validation.
• Simulation of active fires Decision support and
  the computation-based control under given
  conditions.
• Simulation of potential fires prevention
  Analyses of the possibility of their suppression
  under various conditions.

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Additional models used in FARSITE

• Crown fire model
• Acceleration model
• Spotting model
• Fuel moisture model
• Postfrontal combustion model

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Input data

• Topography data (GIS)
• - elevation, slope, aspect
• Fuel data (GIS)
• - surface fuel model, canopy cover, stand
  height,
• crown base height, crown bulk density
• Meteorological data (Text)
• - wind direction, wind speed, temperature,
  
• relative humidity, precipitation

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Surface Fuel Model Data

• Fuel loading
• - the mass of the fuel per unit area grouped
  by the particle size classes (1h, 10h, 100h dead
  fuel, live woody, live herbaceous)
• Surface area to volume ratio of each size group
• Fuel depth (m)
• Moisture of extinction ()
• Heat content of the dead and live fuel (kJ.kg-1 )

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Output Data

• Raster files, ARCVIEW Shapefiles, vector files
  (.vct)
• Graphs, tables, pictures

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Forest Fire in the Slovenský Raj National Park
(23.10.2000)

• The burnt area 64 ha
• 6 volunteers lost their lives
• Cost of the fire protection 5,8 mil. Sk
• Damage 356 mil. Sk
• ----------------------
• Topography hills and valleys
• Cover conifers (spruce, fir) 80
  
• maple, beech
  20

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Assumptions of our simulation

• Real data for topography (elevation, aspect,
  slope) and canopy cover (TU Zvolen)
• Original fuel model TER, elaborated by intensive
  terrain measurements (TU Zvolen)
• Meteorological data for wind, temperature and
  humidity from meteorological stations in Poprad
  and Telgart (TU Zvolen)

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The Results of our Simulation
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Real Fire Behavior